Data linkage algebra, data linkage dynamics, and priority rewriting

We introduce an algebra of data linkages. Data linkages are intended for modelling the states of computations in which dynamic data structures are involved. We present a simple model of computation in which states of computations are modelled as data linkages and state changes take place by means of certain actions. We describe the state changes and replies that result from performing those actions by means of a term rewriting system with rule priorities. The model in question is an upgrade of molecular dynamics. The upgrading is mainly concerned with the features to deal with values and the features to reclaim garbage.Comment: 48 pages, typos corrected, phrasing improved, definition of services replaced; presentation improved; presentation improved and appendix adde

A thread calculus with molecular dynamics

We present a theory of threads, interleaving of threads, and interaction between threads and services with features of molecular dynamics, a model of computation that bears on computations in which dynamic data structures are involved. Threads can interact with services of which the states consist of structured data objects and computations take place by means of actions which may change the structure of the data objects. The features introduced include restriction of the scope of names used in threads to refer to data objects. Because that feature makes it troublesome to provide a model based on structural operational semantics and bisimulation, we construct a projective limit model for the theory.Comment: 47 pages; examples and results added, phrasing improved, references replace

Ada (trademark) projects at NASA. Runtime environment issues and recommendations

Ada practitioners should use this document to discuss and establish common short term requirements for Ada runtime environments. The major current Ada runtime environment issues are identified through the analysis of some of the Ada efforts at NASA and other research centers. The runtime environment characteristics of major compilers are compared while alternate runtime implementations are reviewed. Modifications and extensions to the Ada Language Reference Manual to address some of these runtime issues are proposed. Three classes of projects focusing on the most critical runtime features of Ada are recommended, including a range of immediately feasible full scale Ada development projects. Also, a list of runtime features and procurement issues is proposed for consideration by the vendors, contractors and the government

Research in constraint-based layout, visualization, CAD, and related topics : a bibliographical survey

The present work compiles numerous papers in the area of computer-aided design, graphics, layout configuration, and user interfaces in general. There is nearly no conference on graphics, multimedia, and user interfaces that does not include a section on constraint-based graphics; on the other hand most conferences on constraint processing favour applications in graphics. This work of bibliographical pointers may serve as a basis for a detailed and comprehensive survey of this important and challenging field in the intersection of constraint processing and graphics. In order to reach this ambitious aim, and also to keep this study up-to-date, the authors appreciate any comment and update information

Linkages in South African Economic Development

How can South Africa diversify its industrial sector so that it is less dependent on mineral exports, increases labour absorption and reduces unemployment? This book sheds more light on the structure of South Africa’s economy, its industrial sector and inter-sectoral linkages by simulating an economic geography model of the vertical linkages type, by testing linkage strength econometrically and by analysing industrial policy’s role in shaping its development path. It finds that linkages did play an important role in industrial development in South Africa, yet they have often been reinforced by policy interventions. Industrial policy is still geared to benefit the sectors close to the country’s mineral endowment, and thus contributes to South Africa‘s lopsided industrial development

Statistical Inference for Propagation Processes on Complex Networks

Die Methoden der Netzwerktheorie erfreuen sich wachsender Beliebtheit, da sie die Darstellung von komplexen Systemen durch Netzwerke erlauben. Diese werden nur mit einer Menge von Knoten erfasst, die durch Kanten verbunden werden. Derzeit verfügbare Methoden beschränken sich hauptsächlich auf die deskriptive Analyse der Netzwerkstruktur. In der hier vorliegenden Arbeit werden verschiedene Ansätze für die Inferenz über Prozessen in komplexen Netzwerken vorgestellt. Diese Prozesse beeinflussen messbare Größen in Netzwerkknoten und werden durch eine Menge von Zufallszahlen beschrieben. Alle vorgestellten Methoden sind durch praktische Anwendungen motiviert, wie die Übertragung von Lebensmittelinfektionen, die Verbreitung von Zugverspätungen, oder auch die Regulierung von genetischen Effekten. Zunächst wird ein allgemeines dynamisches Metapopulationsmodell für die Verbreitung von Lebensmittelinfektionen vorgestellt, welches die lokalen Infektionsdynamiken mit den netzwerkbasierten Transportwegen von kontaminierten Lebensmitteln zusammenführt. Dieses Modell ermöglicht die effiziente Simulationen verschiedener realistischer Lebensmittelinfektionsepidemien. Zweitens wird ein explorativer Ansatz zur Ursprungsbestimmung von Verbreitungsprozessen entwickelt. Auf Grundlage einer netzwerkbasierten Redefinition der geodätischen Distanz können komplexe Verbreitungsmuster in ein systematisches, kreisrundes Ausbreitungsschema projiziert werden. Dies gilt genau dann, wenn der Ursprungsnetzwerkknoten als Bezugspunkt gewählt wird. Die Methode wird erfolgreich auf den EHEC/HUS Epidemie 2011 in Deutschland angewandt. Die Ergebnisse legen nahe, dass die Methode die aufwändigen Standarduntersuchungen bei Lebensmittelinfektionsepidemien sinnvoll ergänzen kann. Zudem kann dieser explorative Ansatz zur Identifikation von Ursprungsverspätungen in Transportnetzwerken angewandt werden. Die Ergebnisse von umfangreichen Simulationsstudien mit verschiedenstensten Übertragungsmechanismen lassen auf eine allgemeine Anwendbarkeit des Ansatzes bei der Ursprungsbestimmung von Verbreitungsprozessen in vielfältigen Bereichen hoffen. Schließlich wird gezeigt, dass kernelbasierte Methoden eine Alternative für die statistische Analyse von Prozessen in Netzwerken darstellen können. Es wurde ein netzwerkbasierter Kern für den logistischen Kernel Machine Test entwickelt, welcher die nahtlose Integration von biologischem Wissen in die Analyse von Daten aus genomweiten Assoziationsstudien erlaubt. Die Methode wird erfolgreich bei der Analyse genetischer Ursachen für rheumatische Arthritis und Lungenkrebs getestet. Zusammenfassend machen die Ergebnisse der vorgestellten Methoden deutlich, dass die Netzwerk-theoretische Analyse von Verbreitungsprozessen einen wesentlichen Beitrag zur Beantwortung verschiedenster Fragestellungen in unterschiedlichen Anwendungen liefern kann

Simplified system dynamics: a methodology for corporate modelling

This thesis deals with the development and application of a methodology for constructing corporate planning models. The methodology is based on a framework of general systems concepts consisting of elements from the System Dynamics and Input-Output approaches to the modelling of complex systems. These concepts permit the use of explicit and efficient procedures for constructing corporate planning models, which support each of the conceptual, verbal, graphical and mathematical phases of the model abstraction process. Support for the model programming and computational phases is provided by a system of interactive computer programs, written in the ‘BASIC’ language, for a Digital PDP 11/70 timesharing computer. The technical details of these programs and their use, are contained in the Appendices. Discussion of the methodology is preceded by reviews of both management science and corporate planning, which focus on their respective development histories, future development directions, and their inter-relationship. These reviews provide a foundation for examining the role of computer-based models in corporate planning. In particular, the importance of modelling in resolving the conflicts and problems of corporate planning is established. Following appraisal of a selection of systems-based modelling methodologies, including System Dynamics, a simplified version of this methodology is presented. This version permits the construction of more open models in which priority is accorded to representation of the structured, mechanistic relationships of the system being modelled. Introduction of the matrix algebra concepts of Input-Output Analysis enables systems to be represented as vectorised networks, which in turn facilitate the construction of less aggregated models. A series of ten applications of the simplified System Dynamics methodology, involving the construction of both financial and non-financial models, is then presented. These applications, together with a comparative study using a typical ‘non-systems’ approach to the construction of a benchmark financial model, provide the basis for assessment of the methodology. This assessment is made in terms of its strengths and weaknesses, and of some recent technological advances in computing. As a systems approach to corporate modelling, the methodology is found to meet the needs of corporate planners more closely than any of the existing systems methodologies. The representation of systems as open vectorised networks facilitates model-building and the construction of more flexible, understandable models. These advantages increase markedly as the scale of models constructed with the methodology increases. The weaknesses of simplified System Dynamics are found to relate directly to the limitations of the current version of the computer software system which supports it. This software system must therefore be upgraded if these weaknesses are to be eliminated. This upgrading should proceed in a manner which takes maximum advantage of the data base management and graphics capabilities of modern time-sharing computers